Substation circuit



July 10, 1923.

H. FLETCHER I SUBSTATION CIRCUIT Filed Dec- 15 1920 //7 venfor:

fiara/gy F/e/c/ver Patented July lfl, i923.

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HARVEY FLETQHER, OF NEW YORK, N. Y., ASSIGNOR 'IO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SUBSTATION CIRCUIT.

Application filed December 15, 1920. Serial No. 430,842.

- To all whom it may concern Be it known that I, HARWY FLETCHER, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Substation Circuits, of which the tollowingis a full, clear, concise, and exact description.

The invention relates to a substation signaling circuit and has for an object to prevent side tone in the receiver due to currents generated by the local transmitter.

This is accomplished by automatically switching the receiver out of the circuit when talking and in response tothe locally generated talking currents. The switching apparatus is oi such a nature, however, that talking currents received from a distant station are inefl'ective to operate the switching means whereby the incoming signal will be transmitted to thereceiver.

Advantage is taken of the fact that the mean resistance of a transmitter when quiet is dilierent from its resistance when agitated by sound waves. In circuit with the transmitter is a relay which is so adjusted that it will be operated when the transmitter is agitated by talking and will release when the transmitter is idle. This switching system is employed to eliectively remove the receiver of the subset from the circuit during transmitting and to remove the transmitter from the circuit during receiving.

Aside from the anti-sidetone feature another advantage of this arrangement is that an appreciable gain in transmission can be secured due to the fact that when receiving substantially all of the incoming currents are supplied to the receiver, and when transinitting all of the generated currents are sent to the distant station.

For further details of the invention refer once may be made to the drawings, in which Fig. 1 illustrates diagrammatically a circuit wherein the receiver is ettectively remover from the circuit by including the high resistance in circuit therewith. Fig. 2 is a inodification wherein the receiver is rendered inefiective by short-circuiting it.

I Referring in detail to Fig. 1 of the drawings, the subset comprises the transmitter 1 and the receiver 2 connected in parallel. A sensitive relay 3 is connected in circuit with the transmitter and is wound to a high impe'dance in order to make the loss in transmission due to the relay negligible. Current for the subset is supplied from the battery 4, and direct current from this source is prevented from passing through the receiver by the condenser 5. Then the subset is idle or when receiving current from a distant star tion the relay 3 is not operated, its armature 6 remaining in the position shown to shortcircuit the high resistance 7, thereby connecting the receiver 2 in circuit. This is made possible by reason of the fact that the resistance of the transmitter 1 at thesetimes will have a comparatively low value whereby the potential across the terminals of the relay 3 due to current flowing from the battery 4: will be insufiicient to operate therelay. l/Vhen the transmitter 1 is agitated, however, by sound waves, its resistance is increased and the relay 3 is operated to effectively remove the receiver 2 from the circuit by opening the shunt about the high resistance 7. This operation of the relay 3 also'serves to short circuit the inductance 8 which effectively removes the transmitter from the alternating current circuit when the relay is in its normal condition.

In the modification of Fig. 2, the armature 6 of relay 3, when the subset is in its normal idle condition or when receiving, removes the transmitter 1 from the alternating current circuit by shunting it by the condenser 9. TV hen the relay 3 is operated due to the agitation of the transmitter 1, the re ceiver 2 is short-circuited by the armature 6. When receiving the receiver 2 is inductively connected to the line section 10 by means of the transformer 11 having one winding thereof in circuit with the line and the other winding in the receiver circuit.

The resistance 12 is for the purpose of equalizing the transmission of direct current over the line 10 shown with respect to other similar lines which would be connected to the central battery 4. This feature forms no part of the present invention, but is described and claimed in the application of Bancroft Gherardi, Serial Number 209, 116, filed December 27 1917, systems for the equalization of transmission lines, now Patent No. 1,396,930, granted Nov. 15, 1921.

What is claimed is:

1. The method of operating a substation circuit including a transmitter element for converting sound waves into electric current variations and a receiver element for converting electric current variations into sound waves, which comprises normally maintaining the transmitter element and the receiver element connected in series across a line with the transmitter element shortcircuited for alternating current, and chang ing the circuit connections, in response to operation of the transmitter element, to el fectively connect the transmitter element across the line for locally generated signaling current.

2. Themethod of operating a substation circuit which comprises normally maintaining. the transmitter short-circuited ior alternating current only, and changing the circuit connections to effectively removethe receiver from the circuit in response to voltage dropacross the transmitter when the transmitter is agitated.

3. A line and a substation circuit, aid circuit comprising a transmitter and a re ceiver simultaneously in connection with said line, and said circuit comprising means including a relay connected in shunt to said transmitter, with respect to said line, and responsive to change of mean voltage drop in. the transmitter due to transmitting action of the transmitter for changing the connections of the receiver with respect to the transmitter, when sending, and for changingthe connections of the'transmitter with respect to the line when receiving.

4. A substation circuit comprising a transmitter, a receiver, a relay connected in shunt to said transmitter and responsive to transmitting action of said transmitter for short-circuiting the receiver when transmitting.

5. A. substation circuit comprising a transmitter, a receiver, a transformer for connecting said receiver to a line, and a relay connected in shunt to said transmitter, said relay having an armature which in one position short-circuits said receiver and in another position connects said receiver in circuit with one of the windings of said transformer.

6. A line, a substation circuit connected thereto comprising a transmitter element for converting sound waves into electric current variations and a receiver element for converting electric current variations into sound waves, a circuit of low impedance to alternating current, a direct current relay, connected in shunt relation to said transmitter element with respect to said line, for rendering said receiver element inoperative when sending, and means controlled by said relay for connecting said low impedance circuit in shunt relation to said transmitter element with respect to said line, when receiving.

7. A substation circuit comprising a. transmitter, a receiver, a line, a transformer for connecting said receiver to said line, a condenser and a relay in shunt to said trans mitter having an armature which in one position short-circuits said receiver and in another position connects said condenser in shunt to said transmitter.

In witness whereof, I hereunto subscribe my name this 9th day of December HARVEY FLETCHER. 

